1. Technical Field
The present invention relates to a driving circuit for an electro-optical panel such as an organic EL panel and a driving method thereof, an electro-optical device having the driving circuit of the electro-optical panel, and an electronic apparatus having the electro-optical device.
2. Related Art
A driving circuit for an electro-optical panel such as an organic electroluminescent (EL) panel is incorporated into a substrate of the electro-optical panel so as to serve as an internal circuit for driving scanning lines or data lines by using externally supplied power, or is attached later to the substrate so as to function as an external IC circuit. Such a driving circuit may be deteriorated or broken for various reasons. In particular, a problem is breakdown caused by the stress of electrostatic discharge, that is, electrostatic breakdown, which occurs while the electro-optical device is assembled or transported. At the time of the assembling process, static electricity is generated around the driving circuit or the electro-optical device. When the static electricity is applied to wiring lines-connected to the driving circuit, the driving circuit is deteriorated or broken.
Accordingly, in order to prevent the deterioration and breakdown of the driving circuit due to the static electricity, a protecting circuit is provided in a signal path through which a signal is input/output in the driving circuit (for example, see Japanese Unexamined Patent Application Publication Nos. 10-294383 and 2003-308050). Specifically, the protecting circuit is provided as an input protecting circuit for an input terminal, to which various signals including clock signals, inversion clock signals, and start pulses are input from the outside of the driving circuit. Alternatively, the protecting circuit is provided as an output protecting circuit for an output terminal, through which various signals including scanning signals and end pulses are output to the outside of the driving circuit.
In addition, a technique in which, in an insulating gate-type transistor circuit device, static electricity accumulated in a circuit portion, which is in a floating state, is effectively discharged so as to prevent the breakdown of an element due to the static electricity is proposed (for example, see Japanese Unexamined Patent Application Publication No. 2000-98338).
In the driving circuit for the organic EL panel, a protecting diode is provided at the outside of the driving circuit as a countermeasure against static electricity which penetrates into the driving circuit from the outside. In this case, however, it is difficult to release the static electricity generated at the inside of the driving circuit to the outside of the driving circuit. For example, in a process of forming power supply lines to supply power in order to drive a level shifter, a shift register, or a buffer included in the driving circuit, when resist is removed after the power supply lines are patterned, static electricity may be generated at the power supply lines. The static electricity may cause electrostatic breakdown of the level shifter included and the buffer connected to the level shifter in the driving circuit. This may result in a lowering of the yield in a process of manufacturing the organic EL panel.